1. Field of the Invention
Robotic arms having multiple degrees of freedom of motion, and robots assembled from modular robotic arm subassemblies.
2. Description of Related Art
A variety of robotic arms and robotic systems are known in the material handling and manufacturing arts. Among the more common robots are the gantry robot, the articulated robot, the polar robot, and the Selective Compliant Articulated Robot Arm (SCARA) robot.
The gantry or Cartesian robot may be constructed of two or three linear actuators. The range of the actuators defines the rectangular working envelope for the system. Although some commercial systems are available as complete systems, most Cartesian systems are constructed of individual linear components selected according for the application. Gantry systems can be very large, as well as small enough to fit on a bench
The articulated robot is a robot with rotary joints. The appearance of an articulated robot is the image that commonly comes to mind when one thinks of industrial robots. Articulated robots are most often quite large and capable of handling payloads of up to hundreds of pounds.
The polar robot typically is comprised of two linear axes and a single rotational axis. The axes are usually oriented as a linear vertical axis, a linear radial axis, and a rotational axis. As a result of this arrangement, the polar robot has a cylindrical working envelope. Polar robots are frequently used when the working area can be arranged around the center of the robot. Polar systems are also typically used in more compact systems that are required to fit on a bench workspace.
The SCARA robot is similar to the polar robot in that it comprises a linear vertical axis and rotation axis. However, the SCARA robot uses a combination of links and rotational axes to provide the radial range of motion. By combining control of each joint in the arm links, complex motion trajectories can be obtained. Very large SCARA robots have been made and used, but most are smaller bench-scale systems.
Common to all robot systems, with the exception of the Cartesian robot, is that there are limited commercial offerings of smaller units for small scale use. This can be a barrier in solving certain material handling problems that are small in scale and require high precision. For example, there may be a need to create a robotic system for transferring a glass microscope slide from a slide receptacle to a microscope instrument for analysis, and subsequently removing the glass slide from the microscope and returning it to the receptacle. The available time budget for an engineer to solve the problem may be short, requiring the maximum use of “off-the-shelf” components wherever possible. Currently, a common way to solve the problem would be to purchase some off-the-shelf motorized linear components from a supplier's catalog, and attempt construct a gantry type robot.
However, the solution to the material handling problem may often have to address additional requirements or constraints. For example, in the present microscope slide handling problem, the robot may need to reach around an obstacle in its tool path, or the robot may need to be retracted to its minimum envelope when not in use. A commercial SCARA robot or an articulated could possibly address these aspects of the problem, but they are generally too bulky and expensive to provide a satisfactory solution. Additionally, for example, there may be a present or future need to add an additional axis of motion to the robot, so that it may handle multiple glass microscope slides for increased throughput.
There is therefore an need for a robot which can be quickly assembled from simple, inexpensive modular subassemblies, or modules. There is a need for a versatile robotic module which enables a robotic design to meet the desired function, rather than having to design the robotic system around available components. A robotic system made with the robotic module needs to be capable of having additional axes added without a redesign of the overall system.